Method and Apparatus for Time Alignment upon Time Advance Group Split or Creation

ABSTRACT

This disclosure details example methods and apparatuses for a wireless communication network and for devices operating in such networks that reduce or eliminate the need for performing random access procedures to obtain appropriate Timing Advance, “TA”, values for use with new TA groups that include cells split from an existing TA group and/or new cells not in any existing TA groups defined for a given device. It is advantageously recognized herein that a TA relationship between one or more cells in an old or existing TA group of a device and one or more cells in a new TA group of the device may be known or otherwise estimated, e.g., based on known delay differences, cell sizes, etc. The TA relationship is used to initialize the TA value used for the new group, e.g., by copying or offsetting the current TA value of the old or existing TA group.

RELATED APPLICATIONS

This application claims priority from the U.S. provisional patentapplication filed on 3 Aug. 2012 and assigned App. No. 61/679,160, whichapplication is incorporated herein by reference.

TECHNICAL FIELD

The present invention generally relates to wireless communicationnetworks and particularly relates to time alignment in such networks.

BACKGROUND

The propagation delays between a network base station and individualwireless communication devices transmitting uplink signals to the basestation depends on the respective distances between the individualdevices and the base station. Timing Advance or “TA” techniques providefor an adjustable delay at each wireless communication device, whichcontrols the timing at the device between the start of a receiveddownlink subframe and a transmitted uplink subframe. By dynamicallyadjusting the TA values used by the various devices, the base stationensures that uplink signals from the various devices are time aligned atthe base station. In turn, receiving time-aligned uplink signals frommultiple devices preserves the orthogonality between those uplinksignals, as received at the base station.

In an example configuration, smaller TA values represent less timingadvance and larger TA values represent more timing advance. In turn,more timing advance means less delay at the device between the start ofa received downlink subframe and the corresponding uplink subframetransmission. Thus, devices that are further away from the base stationand have longer signal propagation delays with respect to the basestation use larger TA values, and devices that are closer to the basestation use smaller TA values.

In a known approach, a base station determines the appropriate TA valuefor any given device based on measurements of its uplink signals. Innetworks based on the Long Term Evolution, “LTE”, standard, a UserEquipment, “UE”, obtains initial uplink synchronization in a given cellusing a random access procedure. Here, the term “cell” connotes givenair interface resources within a given geographic coverage area. Thus,two cells may wholly or partly overlap geographically but use differentcarrier frequencies or different frequency subbands within a definedcarrier frequency bandwidth, for example.

In any case, according to known TA value initialization procedures usedto gain initial uplink synchronization with a given cell in the network,the UE transmits a preamble on a Random Access Channel, “RACH”. Thecell's eNodeB—an LTE base station—determines an initial TA value for theUE based on measurements performed on the preamble transmission, and theeNodeB transmits the initial TA value to the UE in a random accessresponse message. The initial TA value is an absolute TA value of 11bits. The eNodeB subsequently adjusts the UE's TA value, as needed, tomaintain the UE in uplink synchronization with the cell. The subsequentadjustments are based on the eNodeB sending Timing Advance CommandMedium Access Control, “MAC”, Control Elements or “CEs”. Thesesubsequent TA commands are 6 bits and represent delta updates to the TAvalue.

The same TA value may be applied by the UE for its uplink transmissionsto a group of cells in the network, where such groups are referred to asTiming Advance Groups or “TAGs”. Each TA group has one TA value and anassociated TA timer. This arrangement complicates evolving servicescenarios, such as those based on Carrier Aggregation, “CA” and/orCoordinated Multi-Point, “CoMP” service.

With CA, more than one carrier is used to serve a UE or other wirelesscommunication device. These multiple carriers are referred to asComponent Carriers or “CCs” and they generally include a Primary Carrierfrom a Primary Cell or “PCell” and at least one Secondary Carrier from aSecondary Cell or “SCell”. Among the several cells involved in CAservice, the Primary Carrier from the PCell serves as a reference oranchor carrier that is used by the UE for radio link failure monitoringand certain other reference functions.

CoMP expands the multiple carrier idea by using a coordinated set ofeNodeBs and/or other transmission/reception points in the network toserve a given UE. In general, at any given time, only a subset of cellswithin a CoMP cluster is used to serve a given UE. However, that subsetdynamically changes as given cells in the CoMP cluster become more orless attractive for use in serving the UE, based on cell loading,changes in the location of the UE relative to the various CoMPtransmission/reception points in the cluster, and other factors.

According to recent agreement in the Third Generation PartnershipProject, “3GPP”, for serving cells that are in the same TAG as the UE'sPCell, the downlink reception timing of the PCell serves as the timingreference. For serving cells in a TAG not containing the UE's PCell, thedownlink reception timing of a serving cell selected by the UE should beused as the downlink timing reference. Also, note that when a UEreceives an initial or subsequent TA command, it starts the TA timerassociated with the TAG for which the TA command was received. The UEconsiders itself to be in uplink synchronization with the cellsbelonging to the TAG associated with the received TA command so long asthe associated TA timer is running Thus, the UE may perform PhysicalUplink Shared Channel, “PUSCH”, and Physical Uplink Control Channel,“PUCCH”, transmissions in those cells.

However, as noted above, if the UE loses uplink synchronization with thecell(s) in a TAG, or wishes to transmit on cell(s) in a new TAG withwhich it has not gained uplink synchronization, the UE must carry outthe aforementioned random access procedure and then use the initial TAvalue returned from the network before performing any PUSCH or PUCCHtransmissions on the cell(s) in the TAG. Such requirements complicateoperation, particularly in scenarios like CoMP, in which a dynamicallychanging mix of cells is used to serve a given UE. Moreover, it isrecognized herein that such requirements result in significantinefficiencies in many practical scenarios involving the creation of newTAGs for a UE or other device operating within a wireless network.

SUMMARY

This disclosure details example methods and apparatuses for a wirelesscommunication network and for devices operating in such networks thatreduce or eliminate the need for performing random access procedures toobtain appropriate Timing Advance, “TA”, values for use with new TAgroups that include cells split from an existing TA group and/or newcells not in any existing TA groups defined for a given device. It isadvantageously recognized herein that a TA relationship between one ormore cells in an old or existing TA group of a device and one or morecells in a new TA group of the device may be known or otherwiseestimated, e.g., based on known delay differences, cell sizedifferences, etc. The TA relationship is used to initialize the TA valueused for the new group, e.g., by copying or offsetting the TA value fromthe old or existing TA group.

As such, rather than a UE or other device having to perform a randomaccess procedure on one or more cells in a new TA group to obtain theappropriate initial TA value for that new TA group, it is taught hereinto use a TA value for the new TA group that is copied from or otherwisederived from an existing or old TA group of the device. Thus, the TAvalue of a new TA group is initialized not by the device making a randomaccess and receiving an initial TA value in return, but rather by thedevice applying a TA value that is copied from or derived from a TAvalue used by the device for an existing or old TA group. The copying orderivation may be performed on the network side or on the device side,and various signaling and processing options are detailed herein forboth cases.

In one example, a wireless communication device, hereafter “device”, isconfigured to perform a method of timing alignment processing for uplinksignal transmissions by the device to one or more cells in a wirelesscommunication network. The method includes the device receiving one ormore messages indicating the creation of a new TA group for the device,and the device correspondingly setting a TA value to be applied at leastinitially for uplink transmissions to cells in the new TA group, basedon a current TA value used for one of the existing TA groups of thedevice, or according to a signaled TA value sent from the network aspart of or in advance of the one or more messages indicating thecreation of the new TA group. Note that the signaled TA value, which maybe implicitly signaled by the network, may be advantageously determinedon the network side, based on copying or modifying one of the TA valuesalready in use by the device.

In a general sense, the network and/or the device initialize the TAvalue to be applied at the device for a new TA group based on a known orestimated TA relationship between one or more cells in an existing TAgroup of the device and one or more cells in the new TA group. Forexample, the new TA group includes one or more cells split from theexisting group, in which case the TA value to be used for the new TAgroup is copied from the existing group, or is calculated based on someoffset relative to the TA value of the existing group.

Thus, in a network-side example, a network node, such as an LTE eNodeBor other network base station, is configured to perform a method oftiming alignment processing that includes sending one or more TAreconfiguration messages to a wireless communication device, to create anew TA group for the device. The new TA group includes one or more cellshaving a known or estimated TA relationship to one or more cells in anexisting TA group of the device. The method advantageously includessignaling a TA value or a TA offset value to the device based on theknown or estimated TA relationship.

The signaled TA value or TA offset value will be used by the device insetting the TA value initially applied to the new TA group, meaning thatthe controlling network node(s) skip ordering the device to perform therandom access procedure that would normally be required for the deviceto obtain initial uplink timing synchronization with the cells in thenew TA group. Based on this advantageous initialization of the TA valueused by the device for the new TA group, the network-side methodincludes sending adjustment commands to the device, as needed,subsequent to the creation of the new TA group, to adjust the TA valueapplied by the device for the new TA group.

Here and elsewhere in this disclosure, “signaling” a TA value or TAoffset value to the device does not necessarily mean that the TA valueor TA offset value itself is signaled. As a non-limiting example, thenetwork node may simply send an index value or other identifiercorresponding to an existing TA group of the device, and the device maybe configured to copy the TA value of the indicated TA group as the TAvalue to be used initially for the new TA group, or to calculate theinitial TA value of the new TA group by applying an offset to theindicated TA group.

Of course, the present invention is not limited to the above featuresand advantages. Indeed, those skilled in the art will recognizeadditional features and advantages upon reading the following detaileddescription, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless communication network in oneembodiment, wherein the depicted base station and wireless communicationdevice are configured to perform the new Timing Advance, “TA”,processing taught herein.

FIG. 2 is a diagram of an example TA relationship between cellsassociated with different nodes in a wireless communication network,which can be exploited as taught herein for TA value initialization.

FIG. 3 is a block diagram of one embodiment of a wireless communicationdevice.

FIG. 4 is a logic flow diagram of one embodiment of a method of TA valueinitialization as implemented by the wireless communication device ofFIG. 3, for example.

FIG. 5 is a block diagram of one embodiment of a network node, which maybe one of the base stations introduced in FIG. 1, for example.

FIG. 6 is a logic flow diagram of one embodiment of a method of TA valueinitialization as implemented by the network node of FIG. 5, forexample.

FIGS. 7 and 8 are logic flow diagrams illustrating example details andvariations for the TA initialization methods of FIGS. 4 and 6.

FIG. 9 is a logic flow diagram illustrating additional example detailsfor a method of TA value initialization at a wireless communicationdevice.

FIG. 10 is a logic flow diagram illustrating additional example detailsfor a method of TA value initialization at a network node.

DETAILED DESCRIPTION

FIG. 1 illustrates a wireless communication network 10, hereafter“network 10”. The network 10 includes a cell 12 that is associated witha base station 14, and further includes another cell 16 associated withanother base station 18. While the base stations 14 and 18 are notnecessarily different, they may be different in terms of their powersand areas of coverage and they may play different roles within theoverall operation of the network 10.

In the non-limiting example of FIG. 1, the network 10 operates as aheterogeneous network, wherein the base stations 14 and 18 are ofdifferent types and wherein the cell 16 associated with the base station18 overlays the cell 12 associated with the base station 14. In sucharrangements, the cell 12 may be referred to as a “macro” cell serving arelatively larger geographic area than that served by the cell 16, whichmay be referred to as a “hotspot” or “micro”, “pico”, or “femto” cell.

In general, the network 10 includes multiple cells 12 and/or 16,supported by multiple corresponding base stations 14 and/or 18. Ofcourse, those skilled in the art will also recognize that the teachingsherein apply to homogeneous network deployments, e.g., where the network10 includes a number of cells 12 and corresponding base stations 14. Inany case, the wireless communication devices 20, hereafter “device 20”or “devices 20”, may be served from one or more of cells 12 and/or 16,in dependence on several factors, including their relative positionswith respect to such cells. For ease of discussion, the phrase “cell 12,16” shall be understood as referring to a cell 12 and/or a cell 16,unless otherwise noted. Similar, the phrase “base station 14, 18” shallbe understood as referring to a base station 14 and/or a base station18, unless otherwise noted.

With that in mind, a given device 20 operating within the network 10uses Timing Advance, “TA” values for synchronizing its uplinktransmissions with respect to individual cells 12, 16, and with respectto groups of such cells 12, 16—i.e., TA groups. Advantageously, one ormore of the depicted base stations 14, 18 and the depicted device 20 areconfigured to implement network-side and device-side methods,respectively, which provide for efficient initialization of the TA valueused for a new TA group. In particular, the base stations 14, 18 and/orthe device 20 initialize the TA value for a new TA group based on aknown or estimated TA relationship between one or more cells in the newTA group and one or more cells in an existing TA group of the device 20.As used here, an “existing” TA group is not necessarily one thatcontinues to be used by the device 20 after creation and initializationof the new TA group; rather the term “existing” means a TA group that isin existence for the device 20 at the time the new TA group is created.Thus, no particular distinction is made herein between the terms “old TAgroup” and “existing TA group” unless needed for clarity.

FIG. 2 illustrates an example TA relationship that may be known orestimated. In the example illustration, a base station 14 is referred toas the diagram as “BS 14” and a base station 18 is referred to “BS 18”.The base station 14 provides service in a cell 12 that is referenced inthe figure as “CELL1”. Similarly, the base station 18 provides servicein a cell 16 that is referenced in the diagram as “CELL2”. Referringback to FIG. 1, momentarily, one sees that CELL1 may be the depictedcell 12 as associated with the base station 14, and that CELL2 may bethe depicted cell 16 as associated with the base station 18.

When the device 20 is operating at the position marked “POS. A” in FIG.1, it may be served only by the base station 14 using a TA value denotedas “TA1” in FIG. 2. However, when the device 20 moves to the positionmarked as “POS. B” in FIG. 1, it may be served on radio links from boththe base station 14 and from the base station 18—i.e., it may receiveand process downlink signals from both CELL1 and CELL2 and transmitsynchronized uplink signals in both such cells. It is recognized hereinthat the TA value appropriate for uplink transmissions in CELL2, denotedas “TA2” in FIG. 2, has a TA relationship to TA1. More particularly inthe example of FIG. 2, uplink signals from the device 20 as received inCELL2 experience a known or estimable processing delay as compared touplink signals that are received in CELL1 directly from the device 20.

In another example, the node 14 offers both CELL1 and CELL2 and the node18 repeats only CELL2—e.g., the node 18 is a frequency-selectiverepeater. At POS. A, the device 20 communicates with the node 14 forCELL1 and CELL2. As such, the device 20 operates with an existing TAgroup that includes CELL1 and CELL2, where that TA group uses a TA valueappropriate for signal propagation between the node 14 and the device20. However, if the device 20 moves to POS. B, it will get CELL1 fromthe node 14 and CELL2 from the node 18. Thus, when moving from POS. A toPOS. B, a TA group split would occur for the device 20, where the CELL2would be moved from the existing TA group, to a new TA group. The TAvalue for the new TA group can be copied from the TA value used for theexisting TA group.

Thus, in an example case, the device 20 operates for some time at POS. Aand uses TA1 to synchronize its uplink transmissions with respect toCELL1, where the base station 14 adjusts TA1 as needed to maintain suchsynchronization. At some later time, the device 20 moves towards POS. B,which triggers the creation of a new TA group for the device 20, wherethe new TA group includes at least CELL2. Advantageously, the known orestimated TA relationship between CELL1 and CELL2 is exploited todetermine the initial value of TA2, for use by the device 20. Doing soeliminates the need for the device 20 to perform a random accessprocedure in CELL2 to obtain an appropriate initial value for TA2. Inone example, the current value of TA1 as last adjusted is copied andused as the initial value for TA2. In another example, anoffset—referred to as a TA offset value—is applied to TA1 and theresulting TA value is used as the initial value of TA2.

The TA offset value corresponds to the known or estimated processingdelay difference associated with CELL2, in relation to CELL1. Ingeneral, such TA offset values may be defined in accordance with 3GPP TS36.211: Physical Channels and Modulation. That is, a TA offset value maybe expressed as a number of TA value steps—i.e., steps of 16T_(S) asdefined in TS 36.211. Of course, other mechanisms for specifying TAvalue offsets are contemplated herein, such as by having a table ofpredefined offset values, and specifying given offsets as table indexvalues.

A base station 14, 18 is configured, for example, with data embodying aknown or expected offset relative to TA1, where that offset representsthe additional delay associated with CELL2 relative to CELL1. Further,multiple delay values may be involved. For example, when the basestation 18 associated with CELL2 is a repeater, the delays involveddepend on whether the repeater is operating in both uplink and downlinkdirections, or only in one direction. The delays to consider aredifferent for the two possibilities. If the repeater is operating inboth the uplink and downlink directions, the delay difference ofinterest is the sum of downlink and uplink processing delays.

The difference in propagation delays for direct communications in CELL1as compared to communicating through CELL2 is expected to be in theorder of a few milliseconds. The base station 14, 18 can be configuredto store a representative or actual value for this delay, as a known orestimated TA relationship between CELL1 and CELL2. Knowledge of theactual or estimated delay differences between cells 12, 16 providessignificant advantages when initializing the TA value of a new TA groupthat includes a cell 12, 16 having a known TA relationship to a cell 12,16 in an old or existing TA group of the device 20. For example, if acell 12, 16 in the new TA group is being split from an existing TA groupof the device 20, it is reasonable to copy the TA value in use for theexisting group as the starting TA value for the new TA group, or toinitialize the TA value by offsetting the TA value of the existinggroup, based on detected misalignment, or some other initial adjustment.Such operations have broad advantages in terms of avoiding the need forrandom access procedures for TA value initialization, and are expectedto yield particularly significant benefits in heterogeneous andrepeater-based network environments, where the mix of cells 12, 16 usedto serve a given device 20 may change relatively frequently.

Broadly, then, it is contemplated herein to determine the TA value for anew TA group based on adjusting the TA value associated with an old orexisting TA group of the device 20. The adjustment may be determined atthe device 20 or in the network 10 as an offset associated withdifferences in processing node delays between the network nodes involvedin the old and new TA groups and/or based on knowledge of networkdeployment details, cell selection criterions, knowledge of other TAvalues in use by the device 20, or TA values known to be associated withor typical for the current location of the device 20, or otherwise basedon positioning information obtained for the device 20.

In a more detailed example, an eNodeB or other type of base station 14,18 uses different criteria for adding a cell 12, 16 to a TA group forthe device 20. For example, the eNodeB may not add a repeater-based cell12, 16 until the repeater signal strength exceeds a relatively highsignal strength threshold, which can be understood as effectivelyshrinking the coverage area of the repeater-based cell 12, 16. With arelatively small coverage area, the initial TA value used for any TAgroup that includes the repeater-based cell 12, 16 may be copied fromthe TA group that includes the cell 12, 16 that is extended by therepeater-based cell 12, 16.

Of further note, the base station 14, 18 in some embodiments “knows” theapproximate position of a device 20 by examining the TA values in use atthe device 20, as each TA value relates to a propagation path distance.Thus, the base station 14, 18 can determine a “suitable” TA value to usefor a new TA group for the device 20, based on knowing the distance ofthe device 20 from the base station 14, 18, or relative to anytransmit/receive node of interest in the network 10. Such distances maybe calculated based on the relationship: TA value=2*distance/speed oflight. The 2*distance term arises because TA values compensate for roundtrip delay—i.e., propagation from a base station 14, 18 to a device 20and back to the base station 14, 18.

FIG. 3 illustrates an example embodiment of a device 20, as contemplatedherein. The device 20 includes one or more receive and transmit antennas22 and an associated transceiver 24 configured to transmit uplinksignals to one or more cells 12, 16 in the network 10 and to receivedownlink signals from one or more cells 12, 16 in the network 10.Accordingly, the transceiver 24 includes a RF receiver 26 and a RFtransmitter 28, which are associated with control and processingcircuits 30, which include one or more baseband processors for transmitand receive signal processing, for example. At least functionally, thecontrol and processing circuits 30—referred to generally as “one or moreprocessing circuits 30” or simply “processing circuits 30”—include a TAvalue determination processing circuit 32.

The one or more processing circuits 30 include, for example, one or moremicroprocessors, microcontrollers, DSPs, FPGAs, ASICs, or other digitalprocessing circuitry that is configured to perform all or part of thedevice-side TA value initialization processing taught herein. Suchprocessing is based, for example, at least in part on the execution ofcomputer program instructions stored in a computer-readable medium, suchas the illustrated memory 34. The memory 34 may further storepreconfigured TA value information 36 and/or signaled TA valueinformation 38, as received from the network 10. Such TA valueinformation is used by the TA value determination processing circuit 32to initialize the TA values for new TA groups, at least for the casewhere the new TA groups include cells 12, 16 having a known or estimatedTA relationship to one or more cells 12, 16 in an existing TA group ofthe device 20.

Thus, the processing circuits 30 are configured to perform timingalignment processing for uplink signal transmissions by the device 20,based on being configured to: receive one or more messages via thetransceiver 24, indicating the creation of a new TA group for the device20; and set the TA value to be applied at least initially for uplinktransmissions to cells 12, 16 in the new TA group, based on a current TAvalue used for one of the existing TA groups of the device 20, oraccording to a signaled TA value sent from the network 10 as part of orin advance of the one or more messages indicating the creation of thenew TA group.

In one example, the processing circuits 30 are configured to follow arule according to which the device 20 sets the TA value of a new TAgroup equal to or offset from the current TA value of the TA group thatincludes a primary cell for the device 20. To the extent that the device20 has more than two existing TA groups defined for it, the processingcircuits 30 would copy the TA value, as last adjusted, for the TA groupthat includes the primary cell, “PCell”, of the device 20, and use thecopied value as the initial value of the TA value to be used for the newTA group. Alternatively, rather than merely copying the TA value of thePCell TA group, the processing circuits 30 calculate the initial valueof the TA value by applying an offset to the TA value of the PCellgroup. In an example, network signaling controls whether the device 20simply copies an existing TA value or offsets an existing TA value, foruse in initializing the TA value of the new TA group.

In a generalized example, the processing circuits 30 are configured toinitialize the TA value of a new TA group to the current TA value in usefor a selected one of the existing TA groups. Alternatively, theprocessing circuits 30 are configured to calculate the TA value for thenew TA group by applying an offset value to the current TA value in usefor a selected one of the existing TA groups. In this and otherexamples, the processing circuits 30 are configured to determine theselected TA group based on a rule preconfigured in the device 20 oraccording to signaling from the network 10.

If the network 10 sends signaling indicating the TA value to be used bythe device 20 as the TA value for a new TA group, the indicated TA valueis referred to as a “default TA value” if the signaling comes in advanceof the network messaging that creates a new TA group. If the indicatedTA value is signaled as part of such messaging, it is referred to as an“explicit TA value”. However, the reader should not confuse the term“explicit TA value” as necessarily meaning explicit signaling of theactual TA value to be used. Whether a default or explicit TA value issignaled by the network 10, the TA value itself may not be signaleddirectly. Instead, the network 10 may signal the TA value by sending anindicator, pointer, or other value that has a known mapping to orassociation with a TA value or TA offset value known to the device 20.

In another embodiment, the processing circuits 30 are configured todetermine a selected TA group according to a configured rule. That is,the device 20 uses a rule to select which one of its existing TA groupsit uses as the basis for setting the initial value of the TA value to beused for the new TA group. In one example, the device 20 copies thecurrent TA value of the selected TA group, for use as the TA valueinitially used for the new TA group. In another example, the device 20calculates the TA value of the new TA group by applying an offset to thecurrent TA value of the selected TA group. As suggested earlier herein,the “rule” may be that the device 20 selects the existing TA group thatincludes the cell 12 or 16 that is operating as the device's PCell.

Because the initialization of the TA value for a new TA group isaccomplished without need for the device 20 performing a random accessprocedure towards one of the cells 12 or 16 in the new TA group, thenetwork 10 can perform adjustments of that TA value subsequent to itsinitialization, as needed—that is, the network 10 can skip ordering thedevice 20 to make a random access for purposes of gaining uplinksynchronization with respect to the cells 12, 16 in the new TA group. Inthis regard, the processing circuits 30 at the device 20 are configuredto adjust the TA value of the new TA group—after initializingit—responsive to subsequent TA adjustment commands signaled from thenetwork 10.

FIG. 4 illustrates one embodiment of a device-side method 400corresponding to the above-described processing configuration of theprocessing circuits 30. The illustrated method 400 of timing alignmentprocessing for uplink signal transmissions by the device 20 to one ormore cells 12, 16 in the network 10 includes: receiving one or moremessages indicating the creation of a new TA group for the device 20(Block 402); and setting the TA value to be applied at least initiallyfor uplink transmissions to the cells 12, 16 in the new TA group, basedon a current TA value used for one of the existing TA groups of thedevice 20, or according to a signaled TA value sent from the network 10as part of or in advance of the one or more messages indicating thecreation of the new TA group (Block 404).

In one variation of the processing represented by Block 404, theprocessing circuits 30 set the TA value of the new TA group equal to acurrent TA value of an existing TA group (Block 404A). In anothervariation, the processing circuits 30 set the TA value of the new TAgroup by calculating the TA value based on applying an offset value tothe current TA value of an existing TA group of the device 20 (Block404B). Note, too, that the device 20 may be capable of performing bothsuch approaches and use one approach at given times and use the otherapproach at other times.

Turning more particularly to the network side of the teachings herein,FIG. 5 illustrates a network node, such as one of the base stations 14,18. In other examples which depend on the type of network 10 involved,the network node may be a base station controller in the Radio AccessNetwork or “RAN”. Further, the network node may be located in a CoreNetwork or “CN” that is associated with the RAN, e.g., a positioningnode or other entity in the CN.

As an example network node, the illustrated base station 14, 18 includesone or more communication interfaces 40, including at least one of: anRF transceiver 42 configured for receiving uplink signals from devices20 operating in one or more cells 12 and/or 16 of the network 10 andtransmitting downlink signals to the one or more devices 20; and aninter-node communication interface 44 configured for communication withone or more other network nodes. The node further includes one or moreprocessing circuits 46, which are broadly referred to as “one or moreprocessing circuits 46” or “processing circuits 46”.

In an example embodiment, the processing circuits 46 at leastfunctionally include a TA value determination processing circuit 48,which is configured to determine the initial TA value for a new TA groupfor a given device 20, based on exploiting a known or estimated TArelationship between one or more cells 12, 16 in an old or existing TAgroup of the device 20 and one or more cells 12, 16 in the new TA group.For clarity, it should be noted that the same TA value is used for allcells 12, 16 in a given TA group, so the initial TA value used for thenew TA group is the same for all cells 12, 16 in the new TA group.However, the TA relationship is not necessarily explicitly known orestimated for every cell 12, 16 in the new TA group, e.g., it may beenough to know the TA relationship between a given cell 12, 16 in thenew TA group and a given one or more cells 12, 16 in the old TA group,and further to know that the initial TA value used for the new TA groupis appropriate for the further cells 12, 16 in the new TA group.

To facilitate using the TA relationship to set the initial TA value ofthe new TA group, the processing circuits 46 include or are associatedwith a computer-readable medium, such as a memory circuit 50 or otherstorage device or unit. The memory circuit 50 stores, for example,computer program instructions that are executed by the processingcircuits 46, to perform the network-side method(s) taught herein. Thememory circuit 50 also may store default and/or explicit TA valueinformation 52 and 54, for use in setting the TA value of a new TAgroup.

These and other architectural details are non-limiting, as otherarrangements can be configured to provide the same or similarfunctionality. In any case, the processing circuits 46 are operativelyassociated with the one or more communication interfaces 40 and areconfigured to: send one or more TA reconfiguration messages to device20, to create a new TA group for the device 20. The new TA groupincludes one or more cells 12, 16 having a known or estimated TArelationship to one or more cells 12, 16 in an existing TA group of thedevice 20. The node exploits the known or estimated TA relationship inthat the processing circuits 46 are configured to signal a TA value or aTA offset value to the device 20 based on the known or estimated TArelationship. The processing circuits 46 are further configured to sendadjustment commands to the device 20, as needed, subsequent to thecreation of the new TA group, to adjust the TA value used for the new TAgroup.

In an example case, the new TA group includes one or more new cells 12,16 and the known or estimated TA relationship comprises a known orestimated path and/or processing delay of the new cell 12, 16 relativeto that of a cell 12, 16 in an existing TA group of the device 20.Correspondingly, the processing circuits 46 are configured to signal theTA value or TA offset value to be used by the device 20 for the new TAgroup based on one of: signaling the TA value as a calculated TA valuedetermined from the current TA value used for the existing group and theknown or estimated delay of the new cell 12 or 16; or signaling the TAoffset value based on the known or estimated delay of the new cell 12 or16.

The new TA group may include cells 12, 16 that are split from anexisting TA group, or it may include one or more new cells 12 and/or 16,or some mix of both. In a scenario where the new TA group includes acell 12 or 16 being split from an existing TA group, the processingcircuits 46 are configured to signal the TA value or TA offset valuebased on one of: signaling the TA value as a value equal to or offsetfrom a current TA value in use for the existing TA group; or signalingthe TA offset value as a value relative to the current TA value in usefor the existing TA group.

As for the new TA group itself, the processing circuits 46 areconfigured to create the new TA group, for example, in response todetecting a timing misalignment for uplink signal transmissions by thedevice 20 to one or more cells 12 or 16 in the existing TA group. Thatis, in one or more embodiments, the processing circuits 46 detect uplinktiming misalignment for one or more cells 12 or 16 in an existing TAgroup of the device 20, and that detection triggers a splitting, whereina new TA group is created for the cells 12 or 16 for which themisalignment was detected and the TA value for the new TA group isadvantageously set according to a known or estimated TA relationshipbetween one or more cells 12 or 16 in the old TA group—the one beingsplit—and one or more cells 12 or 16 in the new TA group.

The known or estimated TA relationship, for example, comprises a knownor estimated difference in processing delays between nodes associatedwith the existing TA group and the new TA group. Referring back to FIG.2, for example, the TA value denoted as TA2 may be determined based atleast in part on a known or estimated extra processing delay incurredfor service through the base station 18 associated with CELL2, ascompared to service directly through the base station 14 associated withCELL1. Such cases apply, for example, when a repeater is used to extendthe coverage of a donor base station. In the same or other embodiments,the known or estimated TA relationship is based at least in part on thecell size of one or more cells 12 or 16 in the new TA group and one ormore cells 12 or 16 in the existing TA group. Thus, the TA relationshipmay partly depend on processing delay as well as on cell size. Forexample, if the new TA group includes a repeater cell 12, 16 that issmall, a suitable TA value for the new TA group may be very similar tothe TA value of an existing TA group that includes the donor cell 12, 16being repeated. However, if the cell size is large, there may be alarger difference between the suitable TA value of the new TA group andthat of the existing TA group.

Consider a scenario where an eNodeB offers two cells 12 or 16, one at800 MHz (large coverage) and one at 2000 MHz. (e.g., a repeater, havinga relatively small coverage area is deployed to extend the coverage ofthe larger cell). The device 20 may be far away from the eNodeB and cantherefore only be configured for the lower frequency, large coveragearea cell. Later, if the device 20 moves into the coverage of therepeater, it can be configured to use the high frequency cell. TheeNodeB may then order that the TA value of the new TA group to be the TAvalue of the old TA group, or as some value offset from the TA value ofthe old TA group.

In a similar scenario, one or more cells 12 or 16 are split from anexisting TA group and logically “moved” to a new TA group that isassociated with a repeater. The eNodeB is aware that some, but notnecessarily all cells 12, 16 are served by the repeater and the eNodeBknows approximately the processing delay of the repeater. Based on thisknowledge, the eNodeB derives an appropriate TA value for the repeatedcell, or an appropriate offset value to be added to the TA value of thenon-repeated cell 12, 16, to obtain a suitable TA value for the device20 to use at least initially for the repeated cell. For example, theeNodeB may be configured to determine the TA value to use initially forthe repeated cell as the TA value of the non-repeated cell plus theknown or estimated processing delay imposed by the repeater, or it maysimply provide offset value information to the device 20, so that device20 can determine the TA value to use at least initially for the repeatedcell 12, 16 by applying the offset to the TA value used by the device 20for the non-repeated cell 12, 16.

In another example, the eNodeB may be configured such that it is notnecessary for the eNodeB to know the processing delay of the repeater.Instead, the eNodeB continuously measures the TA alignment of the device20 on different cells 12, 16, based on determining when uplink signalsfrom the device 20 arrive at the eNodeB for the different cells 12and/or 16. When the device 20 moves in to the coverage of a repeater,the repeated cells will be misaligned and the eNodeB measures themisalignment of the repeated cells and sends an offset to the UE.Alternatively, the eNodeB does not send an offset but instead orders thedevice 20 to set the TA value, at least initially, to the old TA value.Subsequently, the eNodeB sends a TA command, via a MAC control elementor “CE”, which updates the TA value to an appropriate value. That is,the TA value is initialized to the old TA value, and then updated asappropriate.

Broadly, then, in cases where the network 10 knows or can otherwisecalculate the appropriate TA value for the new TA group in advance, thenetwork 10 can be configured to signal the TA value to use for a new TAgroup in advance to the device 20, so that a random access procedure isavoided in the new TA group. In one example, the TA value for the new TAgroup is signaled in the message that creates the new TA group. Inanother example, the TA value for the new TA group is signaled in themessage that specifies the moving cell or cells—i.e., in the messagethat indicates which serving cell(s) are being disassociated from theold TA group and associated with the new TA group and, of course, alsomay indicate one or more new cells to be included in the new TA group.

Notably, where the existing TA group is one among two or more existingTA groups defined for the device 20, the processing circuits 46 areconfigured to signal a TA value or a TA offset value to device 20 bysending an indication to the device 20. The indication indicates whichone of the existing TA groups the device 20 should select for use insetting the TA value initially applied to a new TA group. Here, it willbe understood that the device 20 is configured to set the TA value ofthe new TA group to the current TA value of the selected TA group, or tocalculate the TA value of the new TA group by offsetting the current TAvalue of the selected TA group.

FIG. 6 illustrates an example embodiment of a network-side method 600,which may be performed by a network node, such as the base station 14 or18 illustrated in FIG. 5. The method 600 provides timing alignmentprocessing in the node and includes sending one or more TAreconfiguration messages to device 20 (Block 602), to create a new TAgroup for the device 20. The new TA group includes one or more cells 12and/or 16 having a known or estimated TA relationship to one or morecells 12 and/or 16 in an existing TA group of the device 20.

The method 600 further includes signaling a TA value or a TA offsetvalue to the device 20 based on the known or estimated TA relationship(Block 604). As noted, the signaled TA value or TA offset value will beused by the device 20 in setting the TA value initially applied to thenew TA group. The method 600 therefore includes sending adjustmentcommands to the device 20, as needed, subsequent to the creation of thenew TA group, to adjust the TA value (Block 606).

In some embodiments of the above method, a default TA value is signaledto the device 20 in advance of creating the new TA group. Optionally, anexplicit TA value is signaled to the device 20 in the messaging used tocreate the new TA group. If the device 20 receives this optional,explicit value during such messaging, that explicit TA value isconsidered as overriding the earlier-signaled default TA value—i.e., forthe new TA group being created by the messaging, the device 20 uses theexplicit TA value, or some offset from it, for use with the new TAgroup, rather than using the earlier-signaled default TA value.Conversely, if the device 20 does not receive an explicit TA valueduring the messaging creating a new TA group but earlier received adefault TA value, it applies the default TA value—possibly with someoffset—to the new TA group.

This approach adds flexibility on the network-side, as the network 10can configure the default TA value to a suitable value and not signalexplicit TA values to the device 20, unless there is some need tooverride the default value. In a further variation, a memory or otherstorage in the device 20 contains a pre-configured default value that ituses as the TA value initially applied to a new TA group, unless thenetwork has sent another default TA value to use instead. In thismanner, the device 20 gives preference to the default value signaled bythe network 10, if the network sends such a value, and otherwise usesits “built in” default value.

Such operation suggests some of the flexibility of operation provided bythe teachings herein. FIG. 7 illustrates example combinations ofnetwork-side and device-side processing reflecting such flexibility. Theprocessing flows embodied in FIG. 7 relate to cases involving signalingby the network 10 of the TA value to be applied by a device 20 to a newTA group formed, for example, as a consequence of splitting an old TAgroup. The signaled TA value is sent in advance of the new TA groupcreation, i.e., as a default TA value to be used in the absence of alater-received explicit TA value, or is sent as an explicit TA value aspart of the messaging used to create the new TA group.

It will be appreciated that multiple processing flows may be providedfor in the operational configuration of the involved base stations 14and 18, or other involved network nodes, and in the device 20. Inparticular, in FIG. 7, the following applies:

-   -   “A” denotes the network 10 sending a default TA value to be        applied by a device 20 in case no explicit TA value is signaled        in conjunction with creating a new TA group for the device 20;    -   “B” denotes the detection at the network 10 of a timing        misalignment for the uplink signals from the device 20, with        respect to one or more cells 12, 16 in an existing TA group of        the device 20;    -   “C” denotes the sending of a reconfiguration message from a base        station 14 or 18 in the network 10, to the device 20, ordering        the device 20 to split an existing TA group or to create a new        TA group with one or more new cells 12, 16;    -   “D” denotes the network 10 signaling an explicit TA value to use        for a new TA group being created for the device 20, and it        should be noted that Step “D” can be done in conjunction with        Step “C” or otherwise subsumed into Step “C”;    -   “E” denotes the device 20 applying the default TA value to a new        TA group;    -   “F” denotes the device 20 applying an explicitly signaled TA        value to a new TA group; and    -   “G” denotes the device 20 carrying out TA group reconfiguration        processing.

For example, the processing flow A-B-C-E-G may be followed, wherein thenetwork 10 signals a default TA value to be applied by the device 20 incase no TA value is signaled when an existing TA group is split (BlockA). Subsequently, the network 10 detects that the device's uplinksignals for at least one cell 12, 16 in an existing TA group are notarriving time aligned, which means that the TA value being applied bythe device 20 for that existing TA group is not suitable for all cells12, 16 currently included in that existing TA group (Block B).

In response to the timing misalignment detection, the network 10 signalsa TA group reconfiguration message ordering the device 20 to split theexisting TA group (Block C). Because no explicit TA value was signaledfor the new TA group being created as a consequence of the TA groupsplit, the device 20 applies the default TA value earlier signaled inBlock A to the new TA group (Block E) and performs TA groupreconfiguration processing to reflect the TA group split and thecreation of the new TA group (Block G).

An alternative flow is A-B-D-C-F-G. Blocks A and B are the same asabove, but the flow transitions from Block B to Block D, rather thanBlock C as done in the first flow. Block D comprises the network 10sending an explicit TA value for the device 20 to apply to the new TAgroup. Thus, the network 10 sends the explicit TA value to the device 20and then, as before in Block C, sends a group reconfiguration message(Block C), ordering the device 20 to split the identified existing TAgroup. Because the network 10 signaled an explicit TA value to beapplied to the new TA group, processing continues (Block F) with thedevice 20 using the signaled TA value for the new TA group andperforming TA group reconfiguration accordingly (Block G).

Other possible flows include B-A-C-E-G. This flow is characterized bythe network 10 first detecting the timing misalignment problem (BlockB), then sending a default TA value (Block A), and then sending the TAgroup reconfiguration message (Block C), and so on. Further contemplatedflows include B AD CF G, and B-C-E-G, and B-D-C-F-G.

FIG. 8 illustrates further processing flows contemplated herein, forboth network-side and device-side aspects of the TA value initializationmethod taught herein. As with the example flows illustrated in FIG. 7,FIG. 8 illustrates a number of contemplated processing “flows” based onvarious combinations of processing blocks H through O in which:

-   -   “H” denotes signaling by the network 10 of a default TA offset        value to be used as the initial value for a newly created TA        group, e.g., upon a TA group split;    -   “I” denotes detection by the network 10 that the uplink signals        from a device 20 for at least one cell in an existing TA group        of the device 20 are not arriving time aligned. The TA value for        that existing TA group is therefore not suitable for one or more        cells 12, 16, in the existing TA group;    -   “J” denotes the network 10 signaling a TA group reconfiguration        message ordering the device 20 to split the TA group for which        the timing misalignment was detected;    -   “K” denotes the network 10 sending an explicit offset value for        the new TA group;    -   “L” denotes the device 20 applying the TA value of the old TA        group to the new TA group—here, the old TA group is the group        for which timing misalignment was detected on at least one cell        by the network 10 and the new TA group is the TA group created        by the split of the old TA group;    -   “M” denotes the device 20 applying the TA value of the old TA        group to the new TA group, with an offset set according to a TA        offset value signaled by the network 10;    -   “N” denotes the device 20 applying the TA value of the old TA        group to the new TA group, with an offset set according to a        default offset, e.g., a preconfigured offset stored in the        device 20; and    -   “O” denotes the device 20 performing carrying out TA group        reconfiguration processing.

With the above processing block definitions, FIG. 8 illustrates thefollowing distinct processing flow possibilities: H-I-K-J-M-O;H-I-J-N-O; H-I-J-L-O; I-H-K-J-M-O; I-H-J-N-O; I-H-J-L-O; I-K-J-M-O;I-J-N-O; and I-J-L-O. All such processing flow possibilities offer theadvantage of avoiding random access procedures, for the case where a newTA group includes one or more cells 12, 16 having a known TArelationship to one or more cells 12, 16 in an old or existing TA groupof the device 20. To better appreciate the benefits of avoiding randomaccess procedures for TA value initialization, it must be noted thatperforming random access procedures increases the load of the RACHchannel, costs device battery power and adds processing time.

That is, random access procedures take time to perform, which causesdelays in gaining uplink synchronization for those cells 12, 16 in anewly created TA group. Whenever a device 20 is out of uplinksynchronization with respect to a serving cell 12, 16, schedulingopportunities are lost and that loss negatively impacts the userexperience. Furthermore, with any random access procedure there is arisk for random access failure in which case a new random accessprocedure needs to be performed. Avoiding performing random accessprocedures will therefore lessen RACH load, decrease power consumptionat the device 20 and shorten delays, all improving the user experienceand overall system performance.

FIG. 9 illustrates further processing options for a device 20, accordingto one or more embodiments contemplated herein. The method 900illustrated in FIG. 9 can be understood as an extension or variation ofthe earlier-described method 400 shown in FIG. 4. The method 900includes the device 20 receiving one or more TA group reconfigurationmessages from the network 10 (Block 902), and setting the TA value forthe new TA group using signaled default or explicit TA information, orusing preconfigured information at the device 20 (Block 904). Here, theterm “information” broadly encompasses actual TA values, pointers toactual TA values, actual TA offset values, pointers to actual TA offsetvalues, and essentially any other data item that serves the purpose ofindicating to the device 20 the basis for initializing the TA value ofthe new TA group being created via the TA group reconfigurationmessage(s). As before, “default” TA information is signaled in advanceof the TA group reconfiguration messages, and “explicit” TA informationis signaled as part of the TA group reconfiguration messaging.

The right side of the diagram expands example processing details for theoperations performed in Block 904. Such example processing includesdetermining whether an explicit TA value was received as part of the oneor more TA group reconfiguration messages (Block 904A). If so (YES fromBlock 904A), the device 20 sets the TA value of the new TA group usingthe explicit TA information (Block 904B). If no, (NO from Block 904A),the device 20 determines whether it has default TA information earlierreceived from the network 10 (Block 904C).

If so (YES from Block 904C), the device 20 initializes the TA value ofthe new TA group using the default TA information (Block 904D). If not(NO from Block 904C), the device 20 initializes the TA value of the newTA group using preconfigured TA information (Block 904E). Thepreconfigured information may be a preconfigured TA offset value thatthe device 20 applies to the TA value of one of its existing TA groups,as one example.

In a more particular, example, the device 20 is configured to apply a TAoffset value—known from the network 10 or from preconfigured informationat the device 20—to the TA value in use at the device 20 for a TA groupthat is being split by the network 10. As noted earlier herein, thenetwork 10 may split an existing TA group of the device 20 in responseto detecting timing misalignment for one or more cells 12, 16 in thatexisting TA group. FIG. 10 illustrates this approach from the networkperspective, where such processing is carried out in one of the basestations 14, 18 for example.

The method 1000 illustrated in FIG. 10 includes: detecting uplink timingmisalignment for the uplink signals from a device 20, with respect toone or more cells 12, 16 in an existing TA group of the device 20 (Block1002); sending one or more TA group reconfiguration messages to thedevice 20, to split out the “misaligned” cells 12, 16 into a new TAgroup (Block 1004); and signaling TA value information—explicit ordefault—to the device 20, for use at the device 20 in setting the TAvalue for the new TA group (Block 1006).

Notably, modifications and other embodiments of the disclosedinvention(s) will come to mind to one skilled in the art having thebenefit of the teachings presented in the foregoing descriptions and theassociated drawings. For example, the references to UEs and to LTE-basednetworks should be understood as non-limiting examples. The same methodscan be applied in a range of wireless communication network and devicetypes, such that the network base stations and the correspondingwireless communication devices are configured according to the teachingsherein.

1-37. (canceled)
 38. A method of timing alignment processing for uplinksignal transmissions by a wireless communication device to one or morecells in a wireless communication network, the method comprising:receiving one or more messages indicating the creation of a new TimingAdvance (TA) group for the device; and setting a TA value to be appliedat least initially for uplink transmissions to cells in the new TAgroup, based on a current TA value used for one of the existing TAgroups of the device, or according to a signaled TA value sent from thenetwork as part of or in advance of the one or more messages indicatingthe creation of the new TA group.
 39. The method of claim 38, whereinsetting the TA value comprises setting the TA value equal to or offsetfrom the current TA value of the existing TA group that includes aprimary cell for the device.
 40. The method of claim 39, wherein settingthe TA value comprises calculating the TA value by applying an offsetvalue to the current TA value in use for the existing TA group thatincludes the primary cell for the device.
 41. The method of claim 38,wherein setting the TA value comprises setting the TA value equal to thecurrent TA value in use for a selected one of the existing TA groups.42. The method of claim 38, wherein setting the TA value comprisescalculating the TA value by applying an offset value to the current TAvalue in use for a selected one of the existing TA groups.
 43. Themethod of claim 41, further comprising determining the selected TA groupbased on receiving signaling from the network indicating the selected TAgroup.
 44. The method of claim 41, further comprising determining theselected TA group according to a configured rule.
 45. The method ofclaim 42, further comprising receiving the offset value via signalingfrom the network.
 46. The method of claim 38, further comprisingreceiving the signaled TA value as a default TA value sent in advance ofthe one or more messages, or as an explicit TA value sent in the one ormore messages, and setting the TA value to the default or explicit TAvalue.
 47. The method of claim 38, further comprising adjusting the TAvalue responsive to subsequent TA adjustment commands signaled from thenetwork.
 48. A wireless communication device comprising: a transceiverconfigured to transmit uplink signals to one or more cells in a wirelesscommunication network and to receive downlink signals from one or morecells in the network; and one or more processing circuits configured toperform timing alignment processing for uplink signal transmissions bythe device, based on being configured to: receive one or more messagesvia the transceiver, indicating the creation of a new Timing Advance(TA) group for the device; set a TA value to be applied at leastinitially for uplink transmissions to cells in the new TA group, basedon a current TA value used for one of the existing TA groups of thedevice, or according to a signaled TA value sent from the network aspart of or in advance of the one or more messages indicating thecreation of the new TA group.
 49. The device of claim 48, wherein theone or more processing circuits are configured to set the TA value equalto or offset from the current TA value of the TA group that includes aprimary cell for the device.
 50. The device of claim 49, wherein the oneor more processing circuits are configured to set the TA value bycalculating the new TA based on applying an offset value to the currentTA value in use for the existing TA group that includes the primary cellfor the device.
 51. The device of claim 48, wherein the one or moreprocessing circuits are configured to set the TA value to the current TAvalue in use for a selected one of the existing TA groups.
 52. Thedevice of claim 48, wherein the one or more processing circuits areconfigured to calculate the TA value by applying an offset value to thecurrent TA value in use for a selected one of the existing TA groups.53. The device of claim 51, wherein the one or more processing circuitsare configured to determine the selected TA group based on signalingfrom the network.
 54. The device of claim 51, wherein the one or moreprocessing circuits are configured to determine the selected TA groupaccording to a configured rule.
 55. The device of claim 52, wherein theone or more processing circuits are configured to receive the offsetvalue via signaling from the network.
 56. The device of claim 48,wherein the one or more processing circuits are configured to settingthe TA value based on receiving the signaled TA value as a default TAvalue sent in advance of the one or more messages, or as an explicit TAvalue sent in the one or more messages, and setting the TA value to thedefault or explicit TA value.
 57. The device of claim 48, wherein theone or more processing circuits are configured to adjust the TA valueresponsive to subsequent TA adjustment commands signaled from thenetwork.
 58. A method of timing alignment processing in a network nodeconfigured for operation in a wireless communication network, saidmethod comprising: sending one or more Timing Advance (TA)reconfiguration messages to a wireless communication device, to create anew TA group for the device, wherein the new TA group includes one ormore cells having a known or estimated TA relationship to one or morecells in an existing TA group of the device; signaling a TA value or aTA offset value to the device based on the known or estimated TArelationship, wherein the signaled TA value or TA offset value will beused by the device in setting a TA value initially applied to the new TAgroup; and sending adjustment commands to the device, as needed,subsequent to the creation of the new TA group, to adjust the TA value.59. The method of claim 58, wherein the new TA group includes one ormore new cells and the known or estimated TA relationship comprises aknown or estimated delay of the new cell(s) relative to a current TAvalue in use for the existing TA group, and wherein signaling the TAvalue or TA offset value to be used by the device for the new TA groupcomprises: signaling the TA value as a calculated TA value determinedfrom the current TA value in use for the existing group and the known orestimated delay of the new cell(s); or signaling the TA offset valuebased on the known or estimated delay of the new cell(s).
 60. The methodof claim 58, wherein the new TA group includes one or more cells beingsplit from the existing TA group, and wherein signaling the TA value orTA offset value to be used by the device for the new TA group comprises:signaling the TA value as a value equal to or offset from a current TAvalue in use for the existing TA group; or signaling the TA offset valueas a value relative to the current TA value in use for the existing TAgroup.
 61. The method of claim 58, further comprising creating the newTA group responsive to detecting a timing misalignment for uplink signaltransmissions by the device to one or more cells in the existing TAgroup.
 62. The method of claim 58, wherein the known or estimated TArelationship comprises a known or estimated difference in processingdelays between nodes associated with the existing TA group and the newTA group.
 63. The method of claim 58, wherein the known or estimated TArelationship is based at least in part on the cell size of one or morecells in the new TA group and one or more cells in the existing TAgroup.
 64. The method of claim 58, wherein signaling the TA value or theTA offset value comprises signaling an explicit TA value in the one ormore reconfiguration messages, or comprises signaling a default TA valuein advance of the one or more reconfiguration messages.
 65. The methodof claim 58, wherein signaling the TA value or the TA offset valuecomprises signaling an explicit TA offset value in the one or morereconfiguration messages, or comprises signaling a default TA offsetvalue in advance of the one or more reconfiguration messages.
 66. Themethod of claim 58, wherein the existing TA group is one among two ormore existing TA groups, and wherein signaling the TA value or the TAoffset value comprises sending an indication to the device thatindicates which one of the existing TA groups the device should selectfor use in setting the TA value, and wherein the device is configured toset the TA value to the current TA value of the selected TA group, or tocalculate the TA value by offsetting the current TA value of theselected TA group.
 67. A network node configured for operation in awireless communication network, said node comprising: one or morecommunication interfaces, including at least one of: an RF transceiverconfigured for receiving uplink signals from wireless communicationdevices operating in one or more cells of the wireless communicationnetwork and transmitting downlink signals to the one or more wirelesscommunication devices; and an inter-node communication interfaceconfigured for communication with one or more other network nodes; andone or more processing circuits operatively associated with the one ormore communication interfaces and configured to: send one or more TimingAdvance (TA) reconfiguration messages to a wireless communicationdevice, to create a new TA group for the device, wherein the new TAgroup includes one or more cells having a known or estimated TArelationship to one or more cells in an existing TA group of the device;signal a TA value or a TA offset value to the device based on the knownor estimated TA relationship, wherein the signaled TA value or TA offsetvalue will be used by the device in setting a TA value initially appliedto the new TA group; and send adjustment commands to the device, asneeded, subsequent to the creation of the new TA group, to adjust the TAvalue.
 68. The node of claim 67, wherein the new TA group includes oneor more new cells and the known or estimated TA relationship comprises aknown or estimated delay of the new cell(s) relative to a current TAvalue in use for the existing TA group, and wherein the one or moreprocessing circuits are configured to signal the TA value or TA offsetvalue to be used by the device for the new TA group based on one of:signaling the TA value as a calculated TA value determined from thecurrent TA value in use for the existing group and the known orestimated delay of the new cell(s); or signaling the TA offset valuebased on the known or estimated delay of the new cell(s).
 69. The nodeof claim 67, wherein the new TA group includes one or more cells beingsplit from the existing TA group, and wherein the one or more processingcircuits are configured to signal the TA value or TA offset value basedon one of: signaling the TA value as a value equal to or offset from acurrent TA value in use for the existing TA group; or signaling the TAoffset value as a value relative to the current TA value in use for theexisting TA group.
 70. The node of claim 67, wherein the one or moreprocessing circuits are configured to create the new TA group responsiveto detecting a timing misalignment for uplink signal transmissions bythe device to one or more cells in the existing TA group.
 71. The nodeof claim 67, wherein the known or estimated TA relationship comprises aknown or estimated difference in processing delays between nodesassociated with the existing TA group and the new TA group.
 72. The nodeof claim 67, wherein the known or estimated TA relationship is based atleast in part on the cell size of one or more cells in the new TA groupand one or more cells in the existing TA group.
 73. The node of claim67, wherein the one or more processing circuits are configured to signalthe TA value or the TA offset value based on one of: signaling anexplicit TA value in the one or more reconfiguration messages; orsignaling a default TA value in advance of the one or morereconfiguration messages.
 74. The node of claim 67, wherein the existingTA group is one among two or more existing TA groups, and wherein theone or more processing circuits are configured to signal the TA value orthe TA offset value by sending an indication to the device thatindicates which one of the existing TA groups the device should selectfor use in setting the TA value, and wherein the device is configured toset the TA value to the current TA value of the selected TA group, or tocalculate the TA value by offsetting the current TA value of theselected TA group.